1. Field of the Invention
The present invention relates to a process and apparatus for boring a workpiece having a hole which is to be bored over a relatively great long distance in the axial direction, for example, a cylinder block for an engine having a plurality of bearing holes concentrically formed therein at spaced locations for supporting a crankshaft, or a cylinder head for an engine having a plurality of bearing holes concentrically formed therein at spaced locations for supporting a cam shaft.
2. Description of the Prior Art
In boring such a workpiece as disclosed in Japanese Utility Model Publication Kokoku No. 11458/83, it is a conventional practice to support the workpiece with the axis of the hole to be bored being horizontal and to move a horizontally oriented boring bar in a horizontal direction to effect the boring.
However, when the hole to be bored is relatively long in the axial direction, the boring bar is also correspondingly long. For this reason, a deflection may be produced in the boring bar in the portion between the bearing portions due to its own weight to cause a so-called skipping phenomenon and consequently, the working accuracy may be adversely affected. Therefore, the speed of the rotation of the boring bar must be kept r1elatively low, resulting in a low working rate.